The traditional designs of the disposable lighter have three merits, i.e. fighting the fire easily, economy and cheap, and easy operation. Therefore the disposable lighters are very popular.
However, for protecting the safety and benefit of children, starting from 1993 to 1994, the U.S. Consumer Product Safety Commission declared that it should stop selling the traditional disposable lighter. In view of protecting the safety of children, it is absolutely necessary and reasonable to do so. Therefore, the U.S. Consumer Product Safety Commission imposed an important regulation that "Child below 4 years old cannot light the lighter".
Accordingly, various kinds of disposable lighter having switching mechanism for rendering the lighter child resistant are developed. Such switching mechanism provides a switch member requiring the adult user to turn on before permitting an operating lever to be depressed to lift a gas pipe to open a gas release valve while a spark is generated by simultaneous rotation of a striker wheel in engagement with a flint. However, such conventional gas lighters with switching mechanism also bear the drawbacks as follows:
1. Numerous of additional elements of the switching mechanism are required to incorporate with the traditional disposable lighter for ensuring the safety feature thereof Such costly switching mechanism not only increases the cost of the lighter, but also increases the manufacturing procedures of the lighter. PA1 2. During the igniting operation of the gas lighter, initially, an additional step of turning the switch member of the switching mechanism to release the locking of the operating lever is needed for enabling the depressing the operating lever to lift the gas pipe to open the gas release valve, which complicates the manipulation of ignition. PA1 1. The assembly cost is higher because special care and measurement must be applied to ensure the striker wheel is located in a center position of the wheel axle. Especially in the Hwang's patent, the central polygonal hole of the striker wheel must be exactly equal to the size of the polygonal wheel axle. If it is too small, it is impossible to insert the wheel axle therethrough. It is too big, the striker wheel may not be firmly held in center position. How to punch in the polygonal wheel axle through the polygonal hole of the striker wheel and how to ensure the striker wheel located in the central position of the wheel axle become a headache of Hwang's patent. PA1 2. Accordingly, a slight clearance would be existed between the striker wheel and the wheel axle so as to facilitate the polygonal wheel axle to insert through the central polygonal hole of the striker wheel. Normally, the rotation of the wheel axle can drive the striker wheel to rotate with no problem. However, the striker wheel may gradually move aside after using for a period of time. If such condition happens, the center of the striker wheel will not remain aligning with the flint properly, that may unavoidably affect the ignition of the lighter. Malfunction may also occur. The tip of the flint may get stuck between the driving wheel and the striker wheel.
In fact, the normal pressure of a thumb of a 4 years old child is about 1 kg. The maximum pressure of the thumb is not over 1.5 kg. The normal procedure for lighting the disposable lighter is required to press the side and spark wheel so as to spark the flint and light a fire. At the same time, the lever must be pressed down to release the gas (the normal pressure to release gas is 0.5-1 kg). As mentioned above, most of the disposable lighters are incorporated switching mechanism to lock the gas lever or the spark wheel in order to prevent the children from igniting fire. However, children are excellent in learning. Some smart or brilliant children can pay attention and pretend the adult to release such switching mechanism and ignite the fire.
Accordingly, it is not a wise way of trying to lock the spark wheel or the gas lever. A better way to prevent the children from igniting a lighter is to design a safety lighter that the child below 4 years old does not has the enough power to ignite it. A typical example if disclosed in a U.S. Pat. No. 5,096,414 owned by Zellweger, which comprises a stiker wheel acting on a spark stone. The striker wheel is disposed between two plates of greater diameter than and freely rotatable with respect to the wheel. Actuation of this latter is obtained by friction thanks to the deformation of the pulp of the thumb of the user, and may not be driven by a child as the pulp of the finger of children is not sufficiently thick.
U.S. Pat. No. 5,547,370, owned by Hwang, is a further improvement of Zellweger's patent. Similar to Zellweger's patent, Hwang's patent also includes a wheel axle mounted between two upright supports at the top of a butane wheel, two driving wheels mounted around the wheel axle between the upright supports, and a striker wheel fixedly mounted around the wheel axle and disposed in contact with a spring-supported flint below and turned by the driving wheels through the wheel axle to strike the spring-supported flint in producing sparks. The improvement is that the wheel axle is made of polygonal cross section, having two round rods at two opposite ends loosely inserted into a respective axle hole on each upright support so as to ensure a better connection between the striker wheel and the wheel axle.
However, both the Zellweger's and Hwang's patents still bear the following drawbacks: